Known bottle-filling machines, such as the type described in Patent IT-1136276, comprise a vertical-axis carousel conveyor having a number of seats, which are arranged symmetrically about the vertical axis of the conveyor, house respective bottles by means of a horizontal supporting surface, and are connected to the conveyor in fixed positions. Each seat is associated with a filling head, which is fitted to a supporting disk connected to the conveyor so as to slide with respect to and along the vertical axis of the conveyor, and fills a bottle housed in the respective seat as the conveyor rotates. A load cell is interposed between each seat and the conveyor to real-time weigh the bottle as it is being filled. The real-time bottle weight measurement is used to feedback control the respective filling head and so ensure the bottle is filled with exactly the required amount of product. In actual use, an empty bottle is fed into a respective seat on the conveyor at an input station along the periphery of the conveyor, is subsequently filled by the filling head associated with the seat as the conveyor rotates, and is removed from the seat at an output station located along the periphery of the conveyor and downstream from the input station in the rotation direction of the conveyor.
In a known filling machine of the above type, to make a size change, i.e. to adapt the machine to operate with bottles of a different height, the vertical position of the filling heads must be adjusted by moving the supporting disk vertically along the conveyor so that each filling head is positioned, in use, close to the neck of the relative bottle. Sliding the supporting disk vertically with respect to the conveyor, however, is a slow, complicated job, in that the supporting disk is relatively heavy, and therefore cannot be moved manually by an operator, and, what is more, is connected to the tank and all the conduits supplying the product with which the bottles are filled.
To eliminate the above drawback, Patent Application WO9922209 proposes a filling machine, in which, as opposed to a bottom supporting surface for the relative bottle, each seat simply comprises a gripper for engaging and supporting the bottle by the neck. The bottle thus hangs from the gripper, so that each seat can house bottles of different heights with no alteration required, in that the position of the neck of the bottle is constant. In actual use, however, the centrifugal force generated by rotation of the conveyor on the bottle hanging by its neck tends to tilt and oscillate the hanging bottle with respect to the vertical, thus resulting in a random error in the bottle weight measured by a load cell interposed between the gripper and conveyor.